Cryobiopsy is a special method in the field of endoscopy for withdrawing tissue samples from a patient's body and thus not only for facilitating, but also for improving, the diagnosis regarding any symptoms.
The withdrawing process in a cryobiopsy procedure proceeds as follows. A cryoprobe is placed with slight pressure onto the tissue to be examined. The tissue is frozen onto the probe at this point by intensive cooling of the probe head. After a given time, the frozen-on tissue is extracted from the probe by way of a mechanical pull.
The rapid and intensive cooling of the probe head (approx. −50° C.) is achieved by way of the Joule-Thomson effect. This effect draws on the fact that gas cools intensively when it can expand under high pressure through a small nozzle into a large space. This expansion takes place in the probe head. The expansion of the gas produces energy in the form of cold.
Different apparatuses are known for carrying out a cryobiopsy. One such cryosurgical apparatus is described in United States Patent Application Publication No. 2003/0195436 A1. This instrument is particularly suitable for the inspecting and “coring” of tumors. The instrument includes a handle which is connected to a probe. The probe has a probe head having a lance-shaped configuration at its distal end. The probe head may, as described, be intensively cooled. Furthermore, the instrument has a withdrawal cannula. For the purposes of withdrawal, the tissue is speared using the lance or the probe head and frozen solid thereon. A part of the frozen-solid tissue is cut out of the tumour by advancing the withdrawal cannula. The cut-out tissue sample can be withdrawn by detaching the instrument. In order to facilitate the cutting-out process, the device described in US 2003/0195436 A1 includes an accelerating device which is driven by a spring and drives the cannula into the tissue at a predetermined force.
This cryosurgical instrument is not suitable for withdrawing tissue samples at tissue surfaces. Furthermore, it may be used to withdraw only relatively large amounts of tissue. The corresponding method thus causes serious damage to the tissue to be treated.